Methods of encapsulation

ABSTRACT

Methods and apparatuses suitable for depositing low hydrogen content, hermetic, thin encapsulation layers at temperatures less than about 300° C. are provided herein. Methods involve pulsing plasma while exposing a substrate to deposition reactants, and post-treating deposited encapsulation films to densify and reduce hydrogen content. Post-treatment methods include periodic exposure to inert plasma without reactants and exposure to ultraviolet radiation at a substrate temperature less than about 300° C.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/279,310, filed Sep. 28, 2016, and titled “METHODS OF ENCAPSULATION,”which claims benefit of U.S. Provisional Patent Application No.62/333,054, filed May 6, 2016, and titled “METHODS OF ENCAPSULATION,”which is incorporated by reference herein in its entirety and for allpurposes.

BACKGROUND

Semiconductor device fabrication involves formation of memory stacks,which are often sensitive to oxidation and moisture and may notwithstand high temperature operations or exposure to energetic species.As a result, memory stacks are often encapsulated prior to subsequentprocessing. However, conventional methods of depositing encapsulationlayers may damage components of the process chamber, or may damagesubstrate materials. Further, conventional techniques may not be capableof forming sufficiently thin and hermetic layers.

SUMMARY

Provided herein are methods and apparatuses for forming an encapsulationlayer over a memory device. One aspect involves a method ofencapsulating a memory device on a substrate, the method including: (i)exposing the substrate having the memory device to a depositionprecursor and a reactant at a substrate temperature less than 300° C.;and (ii) igniting a plasma to deposit an encapsulation layer over thememory device, the encapsulation layer being hermetic and having ahydrogen content less than 15%.

In various embodiments, the method further includes exposing theencapsulation layer to a post-treatment process at a temperature lessthan 300° C.

For example, in some embodiments, the post-treatment process includesexposing the substrate to a post-treatment gas and igniting a secondplasma without a reactant. The substrate may be exposed to thepost-treatment gas and the second plasma for a duration between about 10seconds and about 50 seconds. In some embodiments, the post-treatmentgas is any one of nitrogen, ammonia, helium, argon, and combinationsthereof. The method may further include repeating (i) and (ii) to formthe encapsulation layer.

In another example, in some embodiments, the post-treatment processincludes exposing the substrate to ultraviolet radiation. Ultravioletradiation may be emitted at a wavelength between about 180 nm and about600 nm for a duration between about 60 seconds and about 600 seconds.

In various embodiments, the encapsulation layer deposited is any one ofsilicon nitride, undoped silicon carbide, oxygen-doped silicon carbide,germanium nitride, undoped germanium carbide, and oxygen-doped germaniumcarbide.

In various embodiments, the method includes pulsing the plasma todeposit the encapsulation layer. The pulses of plasma may have a pulseduration between about 0.02 ms and about 5 ms. The plasma may be pulsedat a pulsing frequency between about 100 Hz and about 6 Hz. In someembodiments, the plasma is generated in-situ. In some embodiments, thedeposition precursor is a silicon-containing precursor or agermanium-containing precursor.

In various embodiments, the encapsulation layer is deposited by remoteplasma enhanced chemical vapor deposition. For example, in someembodiments, the plasma is generated in a region upstream from andseparate from a processing region where the substrate is housed. In someembodiments, the remote plasma enhanced chemical vapor depositionincludes: (a) flowing the reactant to a remote plasma-generating regionand igniting the plasma to generate reactant radicals; (b) introducingthe reactant radicals through a showerhead to the substrate; and (c)introducing the deposition precursor downstream of the showerhead to thesubstrate while introducing the reactant radicals. The substrate may beprocessed in a chamber having a chamber pressure between about 1.5 Torrand about 7 Torr.

In various embodiments, the memory device is a magnetoresistiverandom-access memory. In various embodiments, the memory device includesa magnetic tunnel junction.

The encapsulation layer may be deposited to a thickness between about 50Å and about 500 Å. In some embodiments where a post-treatment process isused, the post-treatment process may be performed after theencapsulation layer is deposited to a thickness between about 20 Å andabout 50 Å.

In various embodiments, the encapsulation layer is deposited by plasmaenhanced chemical vapor deposition. The encapsulation layer depositedover the memory device may have a step coverage between about 70% andabout 90%. In various embodiments, the substrate is patterned withfeatures having an aspect ratio between about 1.5:1 and about 20:1.

The encapsulation layer may be a silicon nitride film deposited byexposing the substrate to a silicon-containing precursor and anitrogen-containing reactant. In some embodiments, the encapsulationlayer is a silicon carbide film deposited by exposing the substrate to asilicon- and carbon-containing precursor and hydrogen.

The method may further include prior to depositing the encapsulationlayer, heating the substrate to a temperature of about 300° C.

Another aspect involves a method of encapsulating a memory device on asubstrate, the method including (i) exposing the substrate to adeposition precursor and a reactant at a substrate temperature less thanabout 300° C.; and (b) pulsing a plasma for a duration between about0.02 ms and about 5 ms at a pulsing frequency between about 100 Hz andabout 6 Hz when the substrate is exposed to deposition reactants to forman encapsulation layer, such that the formed encapsulation layer is anyone of silicon nitride, undoped silicon carbide, oxygen-doped siliconcarbide, germanium nitride, undoped germanium carbide, and oxygen-dopedgermanium carbide.

The method may further include, after depositing the film, exposing thefilm to a post-treatment process at a substrate temperature of less thanabout 300° C. to form the encapsulation layer. The post-treatmentprocess may include exposing the substrate to a post-treatment gas andigniting a plasma without a silicon-containing or germanium-containingreactant. In some embodiments, the post-treatment process includesexposing the substrate to ultraviolet radiation.

Another aspect involves a memory device including: a memory stack; ahermetic encapsulation layer deposited over the memory stack andencapsulating the memory stack, the encapsulation layer deposited at asubstrate temperature less than about 300° C. by exposure to adeposition precursor, a reactant, and plasma, the encapsulation layerhaving a hydrogen content less than 15%. In various embodiments, theencapsulation layer has a step coverage of at least 70%. In someembodiments, the exposure may include pulsing the plasma using plasmapulse durations between about 0.02 ms and about 5 ms. The encapsulationlayer may be post-treated using UV exposure at a substrate temperatureless than about 300° C. In some embodiments, the encapsulation layer ispost-treated using exposures to a second plasma with post-treatment gasfor a duration between about 10 seconds and about 50 seconds.

In some embodiments, the encapsulation layer is any one of siliconnitride (SiN), silicon carbide (SiC), oxygen-doped silicon carbide(SiCO), germanium nitride (GeN), germanium carbide (GeC), andoxygen-doped germanium carbide (GeCO).

The encapsulation layer may be deposited using remote plasma chemicalvapor deposition.

Another aspect involves an apparatus for processing a semiconductorsubstrate comprising a semiconductor material, the apparatus including:one or more process chambers, whereby at least one process chambercomprises a heated pedestal for heating the semiconductor substrate; aplasma generator; one or more gas inlets into the process chambers andassociated flow-control hardware; and a controller having at least oneprocessor and a memory, whereby the at least one processor and thememory are communicatively connected with one another, the at least oneprocessor is at least operatively connected with the flow-controlhardware, and the memory stores computer-executable instructions forcontrolling the at least one processor to at least control theflow-control hardware by: (i) setting the pedestal temperature to atemperature less than about 300° C.; (ii) introducing a depositionprecursor and a reactant to the one or more process chambers; and (iii)igniting a plasma in pulses when the deposition precursor and reactantare introduced to the one or more process chambers to form a hermeticencapsulation layer having a hydrogen content less than 15%.

The computer-executable instructions may include instructions forpulsing the plasma in (iii) for pulse durations between about 0.02 msand about 5 ms at a pulsing frequency between about 100 Hz and about 6Hz. In some embodiments, the memory further stores computer-executableinstructions for controlling the at least one processor to at leastcontrol the flow-control hardware by: (iv) after igniting the plasma inpulses, stopping flow of the deposition precursor and the reactant tothe one or more process chambers; (v) introducing an inert gas to theone or more process chamber; and (vi) igniting a plasma for a durationbetween about 10 seconds and about 50 seconds.

In some embodiments, the apparatus also includes an ultravioletradiation source, whereby the memory further stores computer-executableinstructions for controlling the at least one processor to at leastcontrol the flow-control hardware by turning on the ultravioletradiation source.

These and other aspects are described further below with reference tothe drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an example memory stack withencapsulation layer subject to moisture and air exposure.

FIGS. 2A-2C are process flow diagrams depicting operations for methodsin accordance with disclosed embodiments.

FIG. 3 is a timing sequence diagram showing an example of a method inaccordance with certain disclosed embodiments.

FIGS. 4-6 are schematic diagrams of example process chambers forperforming disclosed embodiments.

FIG. 7 is a schematic diagram of an example process tool for performingdisclosed embodiments.

FIG. 8 is a Fourier transform infrared spectrum of films fromexperimental data.

FIG. 9 is a schematic illustration of a substrate with an encapsulationlayer deposited in an experiment conducted in accordance with disclosedembodiments.

FIG. 10 is a Fourier transform infrared spectrum of films fromexperimental data.

FIG. 11 is a Fourier transform infrared spectrum of films fromexperimental data.

FIGS. 12A and 12B are images of substrate with an encapsulation layerdeposited in an experiment conducted in accordance with disclosedembodiments.

FIG. 13A is a graph of hydrogen content of various encapsulation layersdeposited in an experiment.

FIG. 13B is a graph of wet etch rate of various encapsulation layersdeposited in an experiment.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth toprovide a thorough understanding of the presented embodiments. Thedisclosed embodiments may be practiced without some or all of thesespecific details. In other instances, well-known process operations havenot been described in detail to not unnecessarily obscure the disclosedembodiments. While the disclosed embodiments will be described inconjunction with the specific embodiments, it will be understood that itis not intended to limit the disclosed embodiments.

In this application, the terms “semiconductor wafer,” “wafer,”“substrate,” “wafer substrate,” and “partially fabricated integratedcircuit” are used interchangeably. One of ordinary skill in the artwould understand that the term “partially fabricated integrated circuit”can refer to a silicon wafer during any of many stages of integratedcircuit fabrication thereon. A wafer or substrate used in thesemiconductor device industry typically has a diameter of 200 mm, or 300mm, or 450 mm. Unless otherwise stated, the processing details recitedherein (e.g., flow rates, power levels, etc.) are relevant forprocessing 300 mm diameter substrates, or for treating chambers that areconfigured to process 300 mm diameter substrates, and can be scaled asappropriate for substrates or chambers of other sizes.

Semiconductor manufacturing processes involve the fabrication of memorystacks, which often include materials that are sensitive to oxidationand moisture. Further, memory stacks may also include materials thatcannot withstand high temperature operations or exposure to energeticspecies. As a result, memory stacks are typically encapsulated prior tosubsequent processing.

One example of memory is a magnetic random access memory (MRAM), whichincludes a plurality of thin metal layers or films may be sequentiallyetched to form magnetic tunnel junction stacks. A magnetic tunneljunction (MTJ) is composed of a thin dielectric barrier layer betweentwo magnetic materials. Electrons pass through the barrier by theprocess of quantum tunneling. This can serve as a basis formagnetic-based memory. FIG. 1 provides an example of a substrate 101with memory stacks having a magnetic tunnel junction including a firstmagnetic layer 105 a, dielectric layer 105 b, and a second magneticlayer 105 c. Layer 103 is disposed between first magnetic layer 105 aand the substrate 101, and layer 107 may be a barrier layer. Varioussuitable chemistries may be used for each of these layers, and eachlayer may include more than one layer.

Overlying the two stacks is a conformal encapsulation layer 109. Aconventional encapsulation layer 109 may include hydrogen 115, which maydiffuse into the magnetic tunnel junction and cause the formation of anitrogen-containing layer 110. A deficient encapsulation layer 109 mayalso be susceptible to damage 120, which may form when the material isexposed to moisture such as water molecules 130.

Conventional techniques of depositing encapsulation layers areinsufficient to achieve optimal results. For example, encapsulationlayers deposited using conventional techniques result in high hydrogencontent, which may cause diffusion as described above with respect toFIG. 1; low density and hermeticity, which can result in peeling orremoval of the encapsulation layer and insufficient quality to protectthe underlying memory; and low step coverage, such as on the order ofbetween about 30% and about 50% for a via having an aspect ratio of 4:1,which can result in partially exposed sidewalls of the memory materials.

The deposited films are also conformal. Conformality of films may bemeasured by the step coverage. “Step coverage” as used herein iscalculated by dividing the average thickness of the deposited film onthe sidewall by the average thickness of the deposited film at the topof the feature and multiplying it by 100 to obtain a percentage.

To combat some of these issues, techniques have been developed toachieve low hydrogen content in an encapsulation layer, but suchtechniques are often performed at high temperatures, which the memorystack is unable to tolerate, thereby resulting in etching of or damageto the memory, such as the dielectric layer in a magnetic tunneljunction, resulting in uneven memory stacks.

Provided herein are methods and apparatuses for depositing encapsulationlayers having low hydrogen content, high density and hermeticity, andhigh step coverage using techniques performed at a low temperature ofless than about 300° C. Various disclosed embodiments may be performedat a pressure between about 0.1 Torr and about 20 Torr. In manyembodiments, the methods disclosed may be performed at a substratetemperature less than about 300° C., such as about 250° C. or about 200°C., or between about 200° C. and about 250° C. In such embodiments, thepedestal may be set to a temperature of less than about 300° C. tocontrol the substrate temperature. For example, for MRAM and phasechange random access memory (PCRAM) applications, the materials on thesubstrate may be sensitive to high temperatures.

Films may be deposited by plasma enhanced chemical vapor deposition(PECVD) and/or remote plasma enhanced chemical vapor deposition (RPCVD).In various embodiments, films are deposited by exposing a substrate to adeposition precursor and a reactant while pulsing plasma in shortpulses, such as pulses having a pulse duration between about 0.01 ms toabout 5 ms, or between about 0.02 ms and about 5 ms, or between about0.05 ms and about 5 ms, or between about 0.05 ms and about 1.9 ms,between about 0.5 ms and about 1.9 ms. Plasma is pulsed in variousembodiments using a pulsing frequency between about 100 Hz and about 6Hz.

Various embodiments involve deposition followed by one or morepost-treatment processing operations. Post-treatment processingoperations include periodic exposure to inert gas and igniting a plasmaduring exposure to inert gas. For example, in some embodiments, after anencapsulation layer is deposited, the encapsulation layer may be exposedto an argon plasma for a duration between about 10 seconds and about 50seconds. In various embodiments, encapsulation layers may be depositedby cycling between (1) PECVD deposition including short pulsed plasmaand (2) exposures to inert gas and plasma. Another post-treatmentprocessing operation includes exposing the deposited encapsulation layerto ultraviolet radiation at a substrate temperature less than 300° C.

Films deposited by disclosed embodiments have a hydrogen content that isabout 50% to 70% less hydrogen than encapsulation layers deposited byconventional techniques, which typically have a hydrogen content between25% and 35%. In various embodiments, deposited encapsulation films havea hydrogen content between about 10% and 15% by atomic % using FTIR.

Methods described herein may be used to deposit encapsulation layers ofany suitable chemistry, which may include Group IV element nitrides orcarbides, any of which may be doped (such as with oxygen) or undoped. Invarious embodiments, the encapsulation layer may be any of the followingchemistries or any of their combinations: silicon nitride (SiN), siliconcarbide (SiC), oxygen-doped silicon carbide (SiCO), germanium nitride(GeN), germanium carbide (GeC), and oxygen-doped germanium carbide(GeCO).

Disclosed embodiments may be suitable for depositing encapsulationlayers to a thickness between about 50 Å and about 500 Å. For example,an encapsulation layer deposited over an MRAM stack may have a thicknessbetween about 150 Å and about 300 Å. A further example encapsulationlayer deposited over a PCRAM stack may be about 50 Å in thickness.Disclosed embodiments may achieve step coverage greater than about 70%,or greater than about 90%, or between about 70% and about 90%.

FIG. 2A provides a process flow diagram depicting operations that may beperformed in accordance with disclosed embodiments. In operation 201, asubstrate including a memory stack is provided. In various embodiments,the substrate is provided to a process chamber. Example process chambersare further described below with respect to FIGS. 4-6.

The substrate may be a silicon wafer, e.g., a 200-mm wafer, a 300-mmwafer, or a 450-mm wafer, including wafers having one or more layers ofmaterial, such as dielectric, conducting, or semi-conducting materialdeposited thereon. Non-limiting examples of under-layers includedielectric layers and conducting layers, e.g., silicon oxides, siliconnitrides, silicon carbides, metal oxides, metal nitrides, metalcarbides, and metal layers. In some embodiments, the substrate includesa stack such as a magnetic tunnel junction. In some embodiments, thesubstrate includes two or more stacks, each of the stacks includinglayers such as the layers depicted in FIG. 1. The space between stacksmay be narrow such that aspect ratios between stacks may be betweenabout 1:1 and about 60:1, or greater than about 1.5:1, or greater thanabout 4:1, or between about 1.5:1 and 60:1, or between about 1.5:1 and40:1, or between about 1.5:1 and 20:1, such as about 5:1. In someembodiments, the space between stacks may be referred to as a “feature.”A stack may contain non-volatile and ferromagnetic materials such as Co,Fe, Mn, Ni, Pt, Pd, Ru, and combinations thereof (such as CoFe), and mayinclude a dielectric layer such as an MgO layer between two layers offerromagnetic materials. Some stack materials may include any of theabove listed ferromagnetic layers in combination with boron, such asCoFeB.

After operation 201 and prior to operation 203, the substrate may besubject to a “temperature soak” whereby the substrate is heated to theprocess temperature upon which the substrate will be subject to variousoperations as described herein. For example, the methods disclosed maybe performed at a substrate temperature less than about 300° C., such asabout 250° C. or about 200° C., or between about 200° C. and about 250°C. Thus, in some embodiments, the substrate is exposed to a temperaturesoak such that a pedestal holding the substrate in a process chamber maybe set to a temperature of, for example, about 250° C. to heat thesubstrate to the process temperature and stabilize the temperature priorto processing.

In operation 203, an encapsulation layer is deposited on the memorystack. In various embodiments, the encapsulation layer is deposited ontwo or more memory stacks. In many embodiments, the encapsulation layeris deposited as a conformal film.

The encapsulation layer may be deposited by various methods. FIGS. 2Band 2C provide process flow diagrams depicting operations of two examplemethods of depositing an encapsulation layer in accordance withdisclosed embodiments.

Operations of FIG. 2B may be used to perform operation 203 of FIG. 2A.In operation 213 a of FIG. 2B, the substrate may be exposed to adeposition precursor and a reactant continuously at low substratetemperature. For example, in various embodiments, while the substrate isheated at a temperature of less than about 300° C., continuous flows ofa deposition precursor and a reactant may be flowed to a process chamberhousing the substrate.

The encapsulation layer may be deposited using a variety of reactantsdepending on the type of encapsulation layer to be deposited. Forexample, deposition of a silicon nitride encapsulation layer may beperformed by exposing the substrate to a silicon-containing precursorand a nitrogen-containing reactant. In another example, deposition of asilicon carbide precursor may be performed by exposing the substrate toa silicon-containing precursor and a carbon-containing reactant. Inanother example, deposition of an oxygen-doped silicon carbide precursormay be performed by exposing the substrate to a silicon-containingprecursor and an oxygen-and-carbon-containing reactant. In anotherexample, deposition of an oxygen-doped silicon carbide precursor may beperformed by exposing the substrate to a silicon-and-carbon-containingprecursor and hydrogen. In another example, deposition of a germaniumnitride encapsulation layer may be performed by exposing the substrateto a germanium-containing precursor and a nitrogen-containing reactant.In another example, deposition of a germanium carbide precursor may beperformed by exposing the substrate to a germanium-containing precursorand a carbon-containing reactant. In another example, deposition of anoxygen-doped germanium carbide precursor may be performed by exposingthe substrate to a germanium-containing precursor and anoxygen-and-carbon-containing reactant. In another example, deposition ofan oxygen-doped germanium carbide precursor may be performed by exposingthe substrate to a germanium-and-carbon-containing precursor andhydrogen.

A general silicon-containing precursor used in methods described hereinmay have the structure:

where R₁, R₂, and R₃ may be the same or different substituents, and mayinclude silanes, amines, halides, hydrogen, or organic groups, such asalkylamines, alkoxy, alkyl, alkenyl, alkynyl, and aromatic groups.

Example silicon-containing precursors include polysilanes(H₃Si—(SiH₂)_(n)—SiH₃), where n≥1, such as silane, disilane, trisilane,tetrasilane; and trisilylamine:

In some embodiments, the silicon-containing precursor is analkoxysilane. Alkoxysilanes that may be used include, but are notlimited to, the following:

-   -   H_(x)—Si—(OR)_(y) where x=1-3, x+y=4 and R is a substituted or        unsubstituted alkyl group; and    -   H_(x)(RO)_(y)—Si—Si—(OR)_(y)H_(x) where x=1-2, x+y=3 and R is a        substituted or unsubstituted alkyl group.

Examples of silicon-containing precursors include: methylsilane;trimethylsilane (3MS); ethylsilane; butasilanes; pentasilanes;octasilanes; heptasilane; hexasilane; cyclobutasilane; cycloheptasilane;cyclohexasilane; cyclooctasilane; cyclopentasilane;1,4-dioxa-2,3,5,6-tetrasilacyclohexane; diethoxymethylsilane (DEMS);diethoxysilane (DES); dimethoxymethylsilane; dimethoxysilane (DMOS);methyl-diethoxysilane (MDES); methyl-dimethoxysilane (MDMS);octamethoxydodecasiloxane (OMODDS); tert-butoxydisilane;tetramethylcyclotetrasiloxane (TMCTS); tetraoxymethylcyclotetrasiloxane(TOMCTS); triethoxysilane (TES); triethoxysiloxane (TRIES); andtrimethoxysilane (TMS or TriMOS).

In some embodiments, the silicon-containing precursor may be anaminosilane, with hydrogen atoms, such as bisdiethylaminosilane,diisopropylaminosilane, tert-butylamino silane (BTBAS), ortris(dimethylamino)silane. Aminosilane precursors include, but are notlimited to, the following: H_(x)—Si—(NR)_(y) where x=1-3, x+y=4 and R isan organic or hydride group.

In some embodiments, a halogen-containing silane may be used such thatthe silane includes at least one hydrogen atom. Such a silane may have achemical formula of SiX_(a)H_(y) where y≥1. For example, dichlorosilane(H₂SiCl₂) may be used in some embodiments.

Example nitrogen-containing reactants include nitrogen gas and ammoniagas.

Example germanium-containing reactants include any germanium-containingcompound that can react to form a germanium nitride, germanium carbide,or oxygen-doped germanium carbide. Examples include germanes, such asGe_(n)H_(n+4), Ge_(n)H_(n+6), Ge_(n)H_(n+8), and Ge_(n)H_(m), where n isan integer from 1 to 10, and n is a different integer than m. Othergermanium-containing compounds may also be used, e.g., alkyl germanes,alkyl germanium, aminogermanes, carbogermanes, and halogermanes.

Example carbon-containing reactants include tetramethylsilane,trimethylsilane, and bis tributylaminosilane. In some embodiments,silicon carbide or germanium carbide encapsulation layers may bedeposited by reacting a silicon and carbon-containing precursor withhydrogen.

An oxygen-doped carbide may be deposited by using a co-reactant otherthan or in addition to one or more silicon-containing precursors.Examples of such co-reactants include carbon dioxide (CO₂), carbonmonoxide (CO), water (H₂O), methanol (CH₃OH), oxygen (O₂), ozone (O₃),nitrogen (N₂), nitrous oxide (N₂O), ammonia (NH₃), methane (CH₄), ethane(C₂H₆), acetylene (C₂H₂), ethylene (C₂H₄), diborane, and combinationsthereof.

In some embodiments, oxygen and/or carbon dioxide is introduced with theprecursor to alter the composition of the silicon carbide film byremoving carbon from the film or precursor during deposition. In someembodiments, an oxygen-and-carbon-containing reactant such as methanolmay be used.

In various embodiments, to deposit an oxygen-doped silicon carbideencapsulation layer, or an oxygen-doped germanium carbide encapsulationlayer, hydrogen gas may be used as a reactant.

In operation 213 b, while the precursor and reactant are continuouslyflowing, an in-situ plasma may be ignited and pulsed by turning theplasma on and off. The plasma may be ignited at a plasma frequency of13.56 MHz. In some embodiments, the plasma is generated using a dualfrequency radio frequency generator. In some embodiments, the plasma isgenerated using a single frequency radio frequency generator. In variousembodiments, the plasma power for a high frequency plasma is betweenabout 400 W (0.1 W/cm²) and about 5000 W (1.5 W/cm²). In variousembodiments, the plasma power for a low-frequency plasma is betweenabout 400 W (0.1 W/cm²) and about 3000 W (1 W/cm²). The plasma may bepulsed at a pulse frequency between about 2 Hz and about 100 kHz withduty cycle ranging from about 1% to about 95%. The duty cycle is definedas the duration for which the plasma is on during a period having aduration T. The duration T includes the duration for pulse ON time (theduration for which the plasma is in an ON state) and the duration forplasma OFF time (the duration from which the plasma is in an OFF state)during a given period. The pulse frequency will be understood as 1/T.For example, for a plasma pulsing period T=100 μs, frequency is 1/T=1/100 μs, or 10 kHz. The duty cycle or duty ratio is the fraction orpercentage in a period T during which the plasma is in the ON state suchthat duty cycle or duty ratio is pulse ON time divided by T. Forexample, for a plasma pulsing period T=100 μs, if a pulse ON time is 70μs (such that the duration for which the plasma is in an ON state in aperiod is 70 μs) and a pulse OFF time is 30 μs (such that the durationfor which the plasma is in an OFF state in a period is 30 μs), the dutycycle is 70%. In some embodiments, the shortest RF on time during thepulse step can be as low as about 5 μsec. In some embodiments, theshortest RF off time can be about 5 μsec. Depending on the duty cycleand the frequency, various combinations of RF on/RF off pulses can beperformed. For example, in some embodiments, this operation may beperformed for a duration of about 0.01 ms to about 5 ms, or betweenabout 0.02 ms and about 5 ms, or between about 0.05 ms and about 5 ms,or between about 0.05 ms and about 1.9 ms, between about 0.5 ms andabout 1.9 ms. During operation 213 b, the plasma may be pulsed hundredsto thousands of time depending on total plasma duration time.

Without being bound by any particular theory, it is believed thatpulsing plasma achieves conditions sufficient to form a conformalencapsulation layer over a substrate with high step coverage. Incontinuous PECVD plasma deposition, when the plasma is on, ions,radicals, neutral species, and other reactive species are generated inthe chamber. The presence of ions results in directionality, such thatfilms deposited on sidewalls of a feature may not be deposited uniformlyand may not achieve high step coverage.

In pulsed PECVD deposition as described herein, it is believed that whenthe plasma is turned off after each pulse, reactive species recombine inthe following order: electrons disappear/recombine, ions recombine, andradicals recombine. Since the pulses are extremely short (e.g., plasmais turned on for a short duration, then turned off for a longer durationto allow deposition), when the plasma is turned off, the electrons andions recombine, eliminating the directionality of the ions in depositingthe material. Radicals take a longer time to recombine, so deposition ismainly driven by radicals, rather than ions. Radicals are then able todelve deep into high aspect ratio features (1.5:1-20:1, particularlysuitable for applications greater than 4:1) and deposit a conformal,high step coverage film even at the bottom of the features.

FIG. 2C provides a second example method of depositing an encapsulationlayer in accordance with disclosed embodiments. Operations in FIG. 2Cmay be used to perform operation 203 of FIG. 2A. FIG. 2C may beperformed in any suitable apparatus for remote plasma chemical vapordeposition (RPCVD). One example apparatus is provided in FIG. 6 anddescribed in further detail below.

In operation 223 a of FIG. 2C, a reactant is introduced to aplasma-generating region upstream of a showerhead of a process chamberhousing the substrate. The reactant is introduced to this region togenerate reactant radicals. It will be understood that although theprocess conditions of operation 223 a may be toggled to generate mostlyreactant radicals, some ions, electrons, and other species may begenerated in the plasma. For example, in some embodiments, nitrogen or amixture of nitrogen and hydrogen gas may be delivered to theplasma-generating region and ignited to form a plasma containing mostlyreactant radicals.

In various embodiments, the reactant may be any of thenitrogen-containing reactants, carbon-containing reactants,oxygen-and-carbon-containing reactants, hydrogen, or combinationsthereof as described above with respect to operation 213 a of FIG. 2B,except for ammonia (NH₃) gas, as ammonia gas may be less susceptible toforming reactant radicals in a remote plasma. Note that for depositing asilicon-containing film or a germanium-containing film, the silicon- orgermanium-containing precursor may not be the reactant that is deliveredto the plasma-generating region in this operation.

Note that in some embodiments, the plasma-generating region may be in aremote plasma generator. For example, in some embodiments, acapacitively-coupled plasma generator may be used. The plasma isgenerated by applying a plasma power between about 0 W and about 500 Wat a frequency of 13.56 MHz to the plasma-generating region. The plasmamay be generated using a power density between about 0.1 W/cm² and about1.5 W/cm².

In operation 223 b, the reactant radicals generated from theplasma-generating region are delivered to the process chamber housingthe substrate through the showerhead.

In operation 223 c, a deposition precursor is introduced to thesubstrate downstream of the showerhead to react with the reactantradicals and form an encapsulation layer over the substrate. In someembodiments, the deposition precursor is introduced downstream of theplasma-generating region. The deposition precursor may be flowed orinjected into the process chamber. In various embodiments, thedeposition precursor is delivered via an inlet separate from theshowerhead to the process chamber. The deposition precursor may be anyGroup IV-containing precursor, such as a silicon-containing precursor orgermanium-containing precursor as described above with respect tooperation 213 a of FIG. 2B.

It is believed that reactant radicals delivered from theplasma-generating region may react with the deposition precursor to formcomplex radicals, which deposits onto the substrate surface as anencapsulation layer. It is further believed that since the plasmaspecies delivered to the chamber includes primarily reactant radicals,as opposed to ions, there is little to no ion-induced damage due to ionbombardment on the surface of the substrate. The pressure of the processchamber during deposition may be between about 1.5 Torr and about 7Torr. In some embodiments, the process chamber may have a pressuregreater than about 7 Torr to deposit a more conformal film.

Operations 223 a-223 c may be performed while the substrate in theprocess chamber is heated to a temperature less than about 300° C. Forexample, the encapsulation layer formed in operation 223 c may be formedover a substrate on a pedestal in the process chamber where thetemperature of the pedestal is set to a temperature less than about 300°C., such as about 250° C.

Films deposited using the method of encapsulation described with respectto FIG. 2C may have a high step coverage. For example, for a substratehaving features with an aspect ratio of 8:1, an oxygen-doped siliconcarbide encapsulation layer deposited in accordance with a method suchas described with respect to operations 223 a-223 c may have a stepcoverage greater than about 90%. Such films may also have reducedhydrogen content, which may be due to the mechanism in which the film isdeposited. In various embodiments, such films may have higher qualitysuch that the films are thin, yet hermetic. These films exhibit the samefilm quality on sidewalls, such as on regions abutting a magnetic tunneljunction, as on field regions of the substrate.

Returning to FIG. 2A, in operation 205, an optional post-treatment isperformed. In some embodiments, post-treatment methods described hereinmay be used with conventional PECVD of encapsulation layers to reducehydrogen content and improve the quality of the deposited layers.However, encapsulation layers deposited using conventional PECVD andpost-treated using disclosed embodiments may not yield as high qualityfilms with high step coverage as encapsulation layers deposited usingdisclosed embodiments (such as described above with respect to FIGS. 2Band 2C) and post-treatment embodiments described herein.

In some embodiments, post-treatment may be optional such thatencapsulation layers are deposited using a method such as described withrespect to FIG. 2B or 2C. Encapsulation layers deposited using acombination of a deposition method as described herein and apost-treatment method as described in further detail below may exhibithigher quality, higher step coverage films than films deposited withoutpost-treatment. Examples are described in further detail herein.

Operation 205 may be performed by performing a periodic plasmatreatment, an example of which is depicted in operations 215 a and 215 bof FIG. 2A. Alternatively, operation 205 may be performed by performingan ultraviolet (UV) exposure post-treatment process, which is depictedin operation 225 in FIG. 2A. In some embodiments, the substrate may besubject to one or a combination of both post-treatments. For example, insome embodiments, after depositing an encapsulation layer, the substratemay be exposed to periodic plasma treatment. In some embodiments,operations may be repeated for a substrate including a firstencapsulation layer that is exposed to a periodic plasma treatment suchthat after the periodic plasma treatment, a second encapsulation layermay be deposited over the treated first encapsulation layer. In someembodiments, after depositing an encapsulation layer, the substrate maybe exposed to UV for UV post-treatment. In some embodiments, afterdepositing the encapsulation layer, the substrate may be exposed to aperiodic plasma treatment, and then a UV post-treatment.

In operation 215 a, the substrate including the deposited encapsulationlayer is exposed to a plasma without a silicon-containing orgermanium-containing reactant at a substrate temperature less than about300° C. to treat the deposited encapsulation layer as one method ofperforming a post-treatment process In some embodiments where apost-treatment process is used, the post-treatment process may beperformed after the encapsulation layer is deposited to a thicknessbetween about 20 Å and about 50 Å. In some embodiments, pulsed plasmadeposition as described above with respect to FIG. 2B is performed incombination with operation 215 a such that operation 215 a is performedperiodically. For example, in some embodiments, after operation 203 inFIG. 2A whereby operations 213 a and 213 b of FIG. 2B are performed,flows of a silicon-containing precursor and a reactant are stopped, apost-treatment gas is introduced, and a continuous plasma is ignited totreat the deposited film without a silicon-containing orgermanium-containing reactant. Performing a combination of pulsed PECVDand post-treatment plasma exposure to a post-treatment plasma achieveshigher quality, higher step coverage, and lower hydrogen contentsilicon-containing films than performing pulsed PECVD alone. Althoughconventionally deposited PECVD films deposited using continuous plasmamay be used in combination with post-treatment, such films may not yieldas high a quality of films with high step coverage as films depositedusing a combination of pulsed PECVD and post-treatment. In variousembodiments, where the encapsulation layer is deposited by a pulsedPECVD process as described above with respect to FIG. 2B, plasmaexposure during operation 215 a may be longer than each plasma pulse ofoperation 213 b of FIG. 2B. For example, in various embodiments, plasmaexposure during operation 215 b may have a duration between about 10seconds and about 50 seconds while each plasma pulse used to deposit theencapsulation layer in operation 203 such as during pulses of operation213 b may have a duration as short as hundredths of a millisecond tomicroseconds. Example pulse durations for plasma pulsing in operation213 b are described above with respect to FIG. 2B.

Further, unlike operation 213 b, during operation 215 a, nosilicon-containing or germanium-containing reactants are flowed to theprocess chamber. Rather, a post-treatment gas such as an inert gas isflowed to the process chamber during operation 215 when the plasma isignited, thereby generating a plasma species that may be capable ofmodifying and densifying the deposited encapsulation layer. Inert gasesmay be selected depending on the type of film to be deposited and thereactants used during the encapsulation layer deposition process. Ageneral list of possible inert gases includes nitrogen, ammonia, andnoble gases such as helium and argon. Gases may be selected depending onthe type of film to be deposited and the reactants used during thedeposition process. The post-treatment gas may include nitrogen only,ammonia only, nitrogen/ammonia mixture, argon only, helium only,argon/helium mixture, and combinations thereof. Other noble gases mayalso be used. In some embodiments, even if nitrogen is used in operation205 to form silicon nitride, operation 207 may involve exposure tonitrogen plasma during post-treatment to reduce hydrogen content anddensify the film. It is believed that periodic exposure to longerdurations of plasma with inert gas reduces hydrogen content of thedeposited encapsulation layer. The upper region of the encapsulationlayer may have reduced hydrogen content. For example, in someembodiments, the top about 25 Å to about 30 Å of the encapsulation layermay have reduced hydrogen content.

In operation 215 b, operations 203-215 a may be optionally repeated suchthat an encapsulation layer is deposited in various cycles, each cycleincluding deposition and post-treatment. Repeated cycles may beperformed to improve the quality of the deposited encapsulation layer.

In operation 225, the substrate may be exposed to UV radiation at asubstrate temperature less than about 300° C. For operation 225, thesubstrate may be transferred from a deposition process chamber to a UVradiation process chamber. An example apparatus is described below withrespect to FIG. 5. UV radiation may be emitted at a wavelength betweenabout 180 nm and about 600 nm for a duration between about 60 secondsand about 600 seconds.

In some embodiments, operation 225 may be performed at a temperaturethat is greater than the substrate temperature used during encapsulationlayer deposition. In some embodiments, if a conventional PECVDencapsulation layer is deposited at a temperature greater than 300° C.,the encapsulation layer may have less hydrogen content than anencapsulation layer deposited at a temperature less than 300° C., but anencapsulation layer deposited at a temperature greater than 300° C. maybe less susceptible to modification by UV treatment and thus UVtreatment may not help reduce the overall hydrogen content of such anencapsulation layer. Thus, UV treatment is suited for embodiments wherethe encapsulation layer is deposited at a temperature less than about300° C.

In some embodiments, the substrate temperature during deposition may bedifferent from the substrate temperature during UV treatment. In someembodiments, where periodic plasma treatment is also used betweendeposition and UV treatment, the substrate temperature during theperiodic plasma treatment may be the same as or different from thesubstrate temperature during deposition. In various embodiments,although the substrate temperatures are different, the substratetemperatures during each operation may be less than about 300° C. Thetemperatures selected for both the deposition and the UV treatment maydepend on the encapsulation layer material being deposited. For example,a germanium-containing encapsulation layer includes germanium-hydrogenbonds, which have lower energy than silicon-hydrogen bonds. Thus, fordeposition and treatment of a germanium-containing encapsulation layer,the deposition may be performed at a higher temperature (such as atabout 300° C.) and be treated with UV radiation at the same, highertemperature because the germanium-containing encapsulation layer,although the layer is deposited at a higher temperature to result in alayer having less hydrogen content than a layer deposited at a lowertemperature, the bond energy between germanium and hydrogen is less thanthe bond energy between silicon and hydrogen, and thus UV radiation iscapable of modifying the germanium-hydrogen bonds of a film deposited ata higher temperature while UV radiation may not be capable of modifyingsilicon-hydrogen bonds of a film deposited at the same temperature.Thus, in some embodiments, for depositing a silicon-containingencapsulation layer, the silicon-containing encapsulation layer may bedeposited at a lower deposition temperature (such as a temperature lessthan about 250° C.) and then subjected to UV radiation at a temperaturesuch as about 300° C.

In one example, an encapsulation layer may be deposited by the methoddescribed above with respect to FIG. 2B, then may be subjected to UVtreatment at a temperature less than about 300° C., such as at about300° C., or about 250° C. In another example, an encapsulation layer maybe deposited by the method described above with respect to FIG. 2C, thenmay be subjected to UV treatment at a temperature less than about 300°C. In another example, an encapsulation layer may be deposited by themethod described above with respect to FIG. 2B, then may be subjected topost-treatment as described with respect to operations 215 a and 215 b,and then may be subjected to UV treatment at a temperature less thanabout 300° C. In another example, an encapsulation layer may bedeposited by the method described above with respect to FIG. 2C, thenmay be subjected to post-treatment as described with respect tooperations 215 a and 215 b, then may be subjected to UV treatment at atemperature less than about 300° C.

FIG. 3 is an example timing sequence diagram showing an example of amethod in accordance with certain disclosed embodiments. Process 300includes a deposition phase 303, a periodic plasma post-treatment phase315, and a UV treatment phase 325. Deposition phase 303 may correspondto operation 203 of FIG. 2A. In this example process 300, depositionphase 303 includes deposition of an encapsulation layer using pulsedPECVD as described above with respect to FIG. 2B. This example process300 is provided as depositing a silicon-containing encapsulation layer.As shown, inert gas may be flowed during the deposition phase 303. Thesilicon-containing precursor is also constantly flowed during depositionphase 303, and the second reactant, which may be any of the reactantsdescribed above with respect to operation 213 a of FIG. 2B, may also beconstantly flowed during deposition phase 303. The plasma may be pulsedas shown in deposition phase 303 such that the plasma is turned on andturned off in short pulses. During this phase, no UV exposure is used.

In periodic plasma post-treatment phase 315, the inert gas may continueto flow. Note that although the inert gas used in process 300 is usedfor the post-treatment as a post-treatment gas for igniting the plasma,in some embodiments the periodic plasma post-treatment may be performedusing a post-treatment gas that is not an inert gas and/or is not thecarrier gas used for delivering process gases. For example, any suitablepost-treatment gas as described above with respect to FIG. 2A may beused to generate the plasma for post-treatment. Periodic plasmapost-treatment phase 315 may correspond to operations 215 a and 215 b ofFIG. 2A. During this phase, the silicon-containing precursor flow andthe second reactant flow are turned off to prevent deposition of anymaterial onto the substrate. The plasma is turned on and turned off fortwo cycles as shown in FIG. 3 as an example. Note that the plasma onduration during each exposure of the periodic plasma post-treatmentphase is longer than the short pulses used during deposition. Note thatalthough two cycles are depicted here, in some embodiments, periodicplasma post-treatment may be performed for one cycle, or may beperformed for two or more cycles. Although UV treatment phase 325immediately follows periodic plasma post-treatment phase 315 in thisexample, in some embodiments another deposition phase may be performedafter periodic plasma post-treatment phase 315. During periodic plasmapost-treatment phase 315, there is no UV exposure.

In UV treatment phase 325, the inert gas may be turned off, and allreactant flows including the silicon-containing precursor and secondreactant flows, are turned off. Here, no plasma is ignited, and only UVradiation is turned on to modify, densify, and/or cure the depositedencapsulation layer. UV treatment phase 325 may correspond to operation225 of FIG. 2A.

Apparatus

Deposition techniques provided herein may be implemented in a plasmaenhanced chemical vapor deposition (PECVD) chamber or a conformal filmdeposition (CFD) chamber or in some embodiments, an atomic layerdeposition (ALD) chamber. Such a chamber may take many forms, and may bepart of an apparatus that includes one or more chambers or reactors(sometimes including multiple stations) such as described in furtherdetail with respect to FIG. 7 that may each house one or more substrateor wafer and may be configured to perform various substrate processingoperations. The one or more chambers may maintain the substrate in adefined position or positions (with or without motion within thatposition, e.g., rotation, vibration, or other agitation). In oneimplementation, a substrate undergoing film deposition may betransferred from one station to another within a chamber (or from onechamber to another within an apparatus) during the process. In otherimplementations, the substrate may be transferred from chamber tochamber within the apparatus to perform different operations, such as UVexposure operations, etching operations, or lithography operations. Thefull film deposition may occur entirely at a single station or anyfraction of the total film thickness for any deposition step. While inprocess, each substrate may be held in place by a pedestal, substratechuck, and/or other substrate-holding apparatus. For certain operationsin which the substrate is to be heated, the apparatus may include aheater, such as a heating plate.

FIG. 4 provides a simple block diagram depicting various reactorcomponents arranged for implementing methods described herein. Reactor400 may be used to deposit encapsulation layers as described herein. Asshown, a reactor 400 includes a process chamber 424 that encloses othercomponents of the reactor and serves to contain a plasma generated by acapacitive-discharge type system including a showerhead 414 working inconjunction with a grounded heater block 420. A high frequency (HF)radio frequency (RF) generator 404 and a low frequency (LF) RF generator402 may be connected to a matching network 406 and to the showerhead414. The power and frequency supplied by matching network 406 may besufficient to generate a plasma from process gases supplied to theprocess chamber 424. For example, the matching network 406 may provide100 W to 1000 W of power. The HFRF component may generally be between 1MHz to 100 MHz, e.g., 13.56 MHz. In operations where there is an LFcomponent, the LF component may be from less than about 1 MHz, e.g., 100kHz. In some embodiments, the plasma may be pulsed for a pulse frequencybetween about 300 Hz and about 1.5 kHz, such as about 500 Hz for a dutycycle. Controller 428 may be configured to set the duration of eachplasma pulse to a duration of about 0.05 ms to about 5 ms, such asbetween about 0.02 ms and about 1.9 ms. In some embodiments, the plasmamay be turned on for periodic plasma treatment as a post-treatment asdescribed herein. For periodic plasma treatment, the plasma may beturned on for a duration between about 10 seconds and about 50 seconds.

Within the reactor 400, a pedestal 418 may support a substrate 416. Thepedestal 418 may include a chuck, a fork, or lift pins (not shown) tohold and transfer the substrate 416 during and between the depositionand/or post-treatment operations. The chuck may be an electrostaticchuck, a mechanical chuck, or various other types of chuck as areavailable for use in the industry and/or for research.

Various process gases may be introduced via inlet 412. For example,gases may include a Group IV-containing precursor such as asilicon-containing precursor or a germanium-containing precursor. Gasesmay include a second reactant, such as hydrogen, a carbon-containingreactant, an oxygen-containing reactant, an oxygen-and-carbon-containingreactant, a nitrogen-containing reactant (such as nitrogen or ammonia),and combinations thereof. In some embodiments, inert gases or carriergases may also be flowed. Example inert gases include argon, helium, andin some cases, nitrogen. In some embodiments, carrier gases are divertedprior to delivering process gases to the process chamber 424.

Multiple source gas lines 410 are connected to manifold 408. The gasesmay be premixed or not. Appropriate valving and mass flow controlmechanisms may be employed to ensure that the correct process gases aredelivered during the deposition and post-treatment phases of theprocess. In the case where a chemical precursor(s) is delivered inliquid form, liquid flow control mechanisms may be employed. Suchliquids may then be vaporized and mixed with process gases duringtransportation in a manifold heated above the vaporization point of thechemical precursor supplied in liquid form before reaching the processchamber 424.

Process gases, such as a silicon-containing precursor ornitrogen-containing gas, may exit process chamber 424 via an outlet 422.A vacuum pump 426, e.g., a one or two stage mechanical dry pump and/orturbomolecular pump, may be used to draw process gases out of theprocess chamber 424 and to maintain a suitably low pressure within theprocess chamber 424 by using a closed-loop-controlled flow restrictiondevice, such as a throttle valve or a pendulum valve.

Apparatus 400 includes a controller 428 which may include one or morememory devices, one or more mass storage devices, and one or moreprocessors. The processor may include a CPU or computer, analog and/ordigital input/output connections, stepper motor controller boards, etc.The apparatus 400 includes system controller 428 employed to controlprocess conditions and hardware states of process tool 400. Thecontroller 428 may be configured to deliver certain process gases atvarious flow rates for certain durations and control plasma frequency,plasma pulse frequency, plasma power, and other process conditions asdescribed herein. The controller 428 may be configured to turn theplasma on and off in accordance with some embodiments. The controller428 may have any of the characteristics of controller 750 describedbelow with respect to FIG. 7.

In some embodiments, an encapsulation layer may be deposited in a remoteplasma chemical vapor deposition (RPCVD) chamber. FIG. 5 presents asimplified view of an apparatus 500 that may be used for certainradical-based processes such as a radical-based encapsulation layerdeposition process. Other radical-based processes and reaction chambersmay also be used in accordance with certain embodiments. Apparatus 500includes a processing chamber 524 which includes chamber walls 503,chamber floor 504, and chamber ceiling 505. Inside the processingchamber 524 is a substrate support 518, on which substrate 516 sits. Theprocessing chamber 524 also includes an inlet 508 and an exhaust outlet509. A remote plasma source 510 is provided above the processing chamber524. The remote plasma source 510 includes a plasma generator (notshown) for generating a plasma within the remote plasma source. Theplasma generator includes hardware (e.g., coils, electrodes, etc.) forproducing a plasma, which may be an inductively coupled plasma, acapacitively coupled plasma, a microwave coupled plasma, etc. The remoteplasma source 510 is separated from the processing chamber 524 by ashowerhead 514 a having a plurality of showerhead holes 514 b. Theremote plasma source 510 has an inlet 512 for providing gas used togenerate the remote plasma. The apparatus 500 includes system controller550 employed to control process conditions and hardware states ofprocess tool 500. The controller 550 may have any of the characteristicsof controller 750 described below with respect to FIG. 7.

In various embodiments, a deposited encapsulation layer may be subjectto ultraviolet (UV) post-treatment as described in disclosedembodiments, for example with respect to operation 225 of FIG. 2A asdescribed above. In some embodiments, the substrate including thedeposited encapsulation layer may be transferred to a chamber for curingor exposing the substrate to UV radiation. FIG. 6 shows a schematicillustration of an example of an exposure chamber 624 for exposing asubstrate 616 to UV. For example, the apparatus 600 shown in FIG. 6 maybe used to perform operation 225 as described above with respect to FIG.2A. Apparatus 600 has a plasma producing portion 611 and an exposurechamber 624 separated by a showerhead assembly or faceplate 614. Insideexposure chamber 624, a platen (or stage) 618 provides a wafer support.Platen 618 is fitted with a heating/cooling element. In someembodiments, platen 618 is also configured for applying a bias tosubstrate 616. Low pressure is attained in exposure chamber 624 viavacuum pump via conduit 607. Sources of gaseous treatment gases providea flow of gas via inlet 612 into plasma producing portion 611 of theapparatus 600. Plasma producing portion 611 may surrounded by inductioncoils (not shown). During operation, gas mixtures are introduced intoplasma producing portion 611, the induction coils are energized and aplasma is generated in plasma producing portion 611. Showerhead assembly614 may have an applied voltage and terminates the flow of some ions andallows the flow of neutral species into exposure chamber 624. Theapparatus 600 includes system controller 650 employed to control processconditions and hardware states of apparatus 600. The controller 650 mayhave any of the characteristics of controller 750 described below withrespect to FIG. 7.

As discussed above, the techniques for deposition and post-treatment ofan encapsulation as discussed herein may be implemented on amulti-station or single station tool. FIG. 7 is a schematic illustrationof an example of such a tool. In specific implementations, a 300 mm LamVector™ tool having a 4-station deposition scheme or a 200 mm Sequel™tool having a 6-station deposition scheme may be used. In someimplementations, tools for processing 450 mm substrates may be used. Invarious implementations, the substrates may be indexed after everydeposition and/or post-deposition plasma treatment, or may be indexedafter etching steps if the etching chambers or stations are also part ofthe same tool, or multiple depositions and treatments may be conductedat a single station before indexing substrates.

FIG. 7 shows a schematic view of an embodiment of a multi-stationprocessing tool 700 with an inbound load lock 702 and an outbound loadlock 704, either or both of which may comprise a remote plasma source. Arobot 706, at atmospheric pressure, is configured to move wafers from acassette loaded through a pod 708 into inbound load lock 702 via anatmospheric port 710. A wafer is placed by the robot 706 on a pedestal712 in the inbound load lock 702, the atmospheric port 710 is closed,and the load lock 702 is pumped down. Where the inbound load lock 702includes a remote plasma source, the wafer may be exposed to a remoteplasma treatment in the inbound load lock 702 prior to being introducedinto a processing chamber 714. Further, the wafer also may be heated inthe inbound load lock 702 as well, for example, to remove moisture andadsorbed gases. In some embodiments, the wafer may be subject to a“temperature soak” as described elsewhere herein in the inbound loadlock 702.

A chamber transport port 716 to processing chamber 714 is opened, andanother robot (not shown) places the wafer into the reactor on apedestal of a first station shown in the reactor for processing. Whilethe embodiment depicted in FIG. 7 includes load locks, it will beappreciated that, in some embodiments, direct entry of a wafer into aprocess station may be provided.

The depicted processing chamber 714 includes four process stations,numbered from 1 to 4 in the embodiment shown in FIG. 7. Each station hasa heated pedestal (shown at 718 for station 1), and gas line inlets. Itwill be appreciated that in some embodiments, each process station mayhave different or multiple purposes. For example, in some embodiments, aprocess station may be switchable between a PECVD deposition mode and aperiodic plasma post-treatment process mode. In some embodiments, aprocess station may be switchable between a chemical vapor deposition(CVD) process mode and a plasma enhanced chemical vapor deposition(PECVD) process mode. In some embodiments, a process station may beswitchable between a PECVD process mode and an RPCVD process mode.Additionally or alternatively, in some embodiments, processing chamber714 may include one or more matched pairs of atomic layer deposition orplasma-enhanced atomic layer deposition process stations. While thedepicted processing chamber 714 includes four stations, it will beunderstood that a processing chamber according to certain disclosedembodiments may have any suitable number of stations. For example, insome embodiments, a processing chamber may have five or more stations,while in other embodiments a processing chamber may have three or fewerstations.

FIG. 7 depicts an embodiment of a wafer handling system 790 fortransferring wafers within processing chamber 714. In some embodiments,wafer handling system 790 may transfer wafers between various processstations and/or between a process station and a load lock. It will beappreciated that any suitable wafer handling system may be employed.Non-limiting examples include wafer carousels and wafer handling robots.FIG. 7 also depicts an embodiment of a system controller 750 employed tocontrol process conditions and hardware states of process tool 700.System controller 750 may include one or more memory devices 756, one ormore mass storage devices 754, and one or more processors 752. One ormore processors 752 may include a CPU or computer, analog and/or digitalinput/output connections, stepper motor controller boards, etc.

In some embodiments, system controller 750 controls all of theactivities of process tool 700. System controller 750 executes systemcontrol software 758 stored in mass storage device 754, loaded intomemory device 756, and executed on processor 752. Alternatively, thecontrol logic may be hard coded in the controller 750. ApplicationsSpecific Integrated Circuits, Programmable Logic Devices (e.g.,field-programmable gate arrays, or FPGAs) and the like may be used forthese purposes. In the following discussion, wherever “software” or“code” is used, functionally comparable hard coded logic may be used inits place. System control software 758 may include instructions forcontrolling the timing, mixture of gases, amount of gas flow, chamberand/or station pressure, chamber and/or station temperature, wafertemperature, target power levels, RF power levels, substrate pedestal,chuck and/or susceptor position, plasma pulse frequency, plasma exposureduration, UV radiation duration, and other parameters of a particularprocess performed by process tool 700. System control software 758 maybe configured in any suitable way. For example, various process toolcomponent subroutines or control objects may be written to controloperation of the process tool components necessary to carry out variousprocess tool processes. System control software 758 may be coded in anysuitable computer readable programming language.

In some embodiments, system control software 758 may includeinput/output control (IOC) sequencing instructions for controlling thevarious parameters described above. Other computer software and/orprograms stored on mass storage device 754 and/or memory device 756associated with system controller 750 may be employed in someembodiments. Examples of programs or sections of programs for thispurpose include a substrate positioning program, a process gas controlprogram, a pressure control program, a heater control program, UVexposure control program, and a plasma control program.

A substrate positioning program may include program code for processtool components that are used to load the substrate onto the pedestaland to control the spacing between the substrate and other parts of theprocess tool.

A process gas control program may include code for controlling gascomposition (e.g., silicon-containing gases, germanium-containing gases,nitrogen-containing gases, carbon-containing gases,oxygen-and-carbon-containing gases, carbon-containing gases,post-treatment gases, and other gases as described herein) and flowrates and optionally for flowing gas into one or more process stationsprior to deposition in order to stabilize the pressure in the processstation. A pressure control program may include code for controlling thepressure in the process station by regulating, for example, a throttlevalve in the exhaust system of the process station, a gas flow into theprocess station, etc.

A heater control program may include code for controlling the current toa heating unit that is used to heat the substrate. Alternatively, theheater control program may control delivery of a heat transfer gas (suchas helium) to the substrate.

A plasma control program may include code for setting RF power levelsapplied to the process electrodes in one or more process stations inaccordance with the embodiments herein.

A UV exposure control program may include code for setting duration ofexposure of UV radiation in one or more process stations in accordancewith the embodiments herein.

A pressure control program may include code for maintaining the pressurein the reaction chamber in accordance with the embodiments herein.

In some embodiments, there may be a user interface associated withsystem controller 750. The user interface may include a display screen,graphical software displays of the apparatus and/or process conditions,and user input devices such as pointing devices, keyboards, touchscreens, microphones, etc.

In some embodiments, parameters adjusted by system controller 750 mayrelate to process conditions. Non-limiting examples include process gascomposition and flow rates, temperature, pressure, plasma conditions(such as RF bias power levels), etc. These parameters may be provided tothe user in the form of a recipe, which may be entered utilizing theuser interface.

Signals for monitoring the process may be provided by analog and/ordigital input connections of system controller 750 from various processtool sensors. The signals for controlling the process may be output onthe analog and digital output connections of process tool 700.Non-limiting examples of process tool sensors that may be monitoredinclude mass flow controllers, pressure sensors (such as manometers),thermocouples, etc. Appropriately programmed feedback and controlalgorithms may be used with data from these sensors to maintain processconditions.

System controller 750 may provide program instructions for implementingthe above-described deposition processes. The program instructions maycontrol a variety of process parameters, such as DC power level, RFpower level, pressure, temperature, plasma pulse frequency, plasmaexposure duration, UV exposure duration, etc. The instructions maycontrol the parameters to operate in-situ deposition of film stacksaccording to various embodiments described herein.

The system controller 750 will typically include one or more memorydevices and one or more processors configured to execute theinstructions so that the apparatus will perform a method in accordancewith disclosed embodiments. Machine-readable media containinginstructions for controlling process operations in accordance withdisclosed embodiments may be coupled to the system controller 750.

In some implementations, a controller 750 is part of a system, which maybe part of the above-described examples. Such systems can comprisesemiconductor processing equipment, including a processing tool ortools, chamber or chambers, a platform or platforms for processing,and/or specific processing components (a wafer pedestal, a gas flowsystem, etc.). These systems may be integrated with electronics forcontrolling their operation before, during, and after processing of asemiconductor wafer or substrate. The electronics may be referred to asthe “controller,” which may control various components or subparts ofthe system or systems. The controller 750, depending on the processingrequirements and/or the type of system, may be programmed to control anyof the processes disclosed herein, including the delivery of processinggases, temperature settings (e.g., heating and/or cooling), pressuresettings, vacuum settings, power settings, radio frequency (RF)generator settings, RF matching circuit settings, frequency settings,flow rate settings, plasma pulse frequency settings, UV exposuresettings, fluid delivery settings, positional and operation settings,wafer transfers into and out of a tool and other transfer tools and/orload locks connected to or interfaced with a specific system.

Broadly speaking, the controller 750 may be defined as electronicshaving various integrated circuits, logic, memory, and/or software thatreceive instructions, issue instructions, control operation, enablecleaning operations, enable endpoint measurements, and the like. Theintegrated circuits may include chips in the form of firmware that storeprogram instructions, digital signal processors (DSPs), chips defined asapplication specific integrated circuits (ASICs), and/or one or moremicroprocessors, or microcontrollers that execute program instructions(e.g., software). Program instructions may be instructions communicatedto the controller in the form of various individual settings (or programfiles), defining operational parameters for carrying out a particularprocess on or for a semiconductor wafer or to a system. The operationalparameters may, in some embodiments, be part of a recipe defined byprocess engineers to accomplish one or more processing steps during thefabrication of one or more layers, materials, metals, oxides, silicon,silicon dioxide, surfaces, circuits, and/or dies of a wafer.

The controller 750, in some implementations, may be a part of or coupledto a computer that is integrated with, coupled to the system, otherwisenetworked to the system, or a combination thereof. For example, thecontroller may be in the “cloud” or all or a part of a fab host computersystem, which can allow for remote access of the wafer processing. Thecomputer may enable remote access to the system to monitor currentprogress of fabrication operations, examine a history of pastfabrication operations, examine trends or performance metrics from aplurality of fabrication operations, to change parameters of currentprocessing, to set processing steps to follow a current processing, orto start a new process. In some examples, a remote computer (e.g. aserver) can provide process recipes to a system over a network, whichmay include a local network or the Internet. The remote computer mayinclude a user interface that enables entry or programming of parametersand/or settings, which are then communicated to the system from theremote computer. In some examples, the controller 750 receivesinstructions in the form of data, which specify parameters for each ofthe processing steps to be performed during one or more operations. Itshould be understood that the parameters may be specific to the type ofprocess to be performed and the type of tool that the controller isconfigured to interface with or control. Thus as described above, thecontroller 750 may be distributed, such as by comprising one or morediscrete controllers that are networked together and working towards acommon purpose, such as the processes and controls described herein. Anexample of a distributed controller for such purposes would be one ormore integrated circuits on a chamber in communication with one or moreintegrated circuits located remotely (such as at the platform level oras part of a remote computer) that combine to control a process on thechamber.

In some embodiments, an apparatus may be provided that is configured toperform the techniques described herein. A suitable apparatus mayinclude hardware for performing various process operations as well as asystem controller 750 having instructions for controlling processoperations in accordance with the disclosed embodiments. The systemcontroller 750 will typically include one or more memory devices and oneor more processors communicatively connected with various processcontrol equipment, e.g., valves, RF generators, substrate handlingsystems, etc., and configured to execute the instructions so that theapparatus will perform a technique in accordance with the disclosedembodiments, e.g., a technique such as that provided in the operationsof FIGS. 2A-2C. Machine-readable media containing instructions forcontrolling process operations in accordance with the present disclosuremay be coupled to the system controller 750. The controller 750 may becommunicatively connected with various hardware devices, e.g., mass flowcontrollers, valves, RF generators, vacuum pumps, etc. to facilitatecontrol of the various process parameters that are associated with thedeposition operations as described herein.

In some embodiments, a system controller 750 may control all of theactivities of the reactor 700. The system controller 750 may executesystem control software stored in a mass storage device, loaded into amemory device, and executed on a processor. The system control softwaremay include instructions for controlling the timing of gas flows,substrate movement, RF generator activation, etc., as well asinstructions for controlling the mixture of gases, the chamber and/orstation pressure, the chamber and/or station temperature, the substratetemperature, the target power levels, the RF power levels, the substratepedestal, chuck, and/or susceptor position, and other parameters of aparticular process performed by the reactor apparatus 700. For example,the software may include instructions or code for controlling the flowrate of a silicon-containing precursor, the flow rate of a reactant, theflow rate of a nitrogen-containing gas, plasma frequency, plasma pulsefrequency, plasma power, UV exposure times, precursor and reactantexposure times, flow rate of post-treatment gas, and UV exposure timesfor each of the above described flow chemistries. The system controlsoftware may be configured in any suitable way. For example, variousprocess tool component subroutines or control objects may be written tocontrol operation of the process tool components necessary to carry outvarious process tool processes. The system control software may be codedin any suitable computer readable programming language.

The system controller 750 may typically include one or more memorydevices 756 and one or more processors 752 configured to execute theinstructions so that the apparatus will perform a technique inaccordance with disclosed embodiments. Machine-readable media containinginstructions for controlling process operations in accordance withdisclosed embodiments may be coupled to the system controller 750.

Without limitation, example systems may include a plasma etch chamber ormodule, a deposition chamber or module, a spin-rinse chamber or module,a metal plating chamber or module, a clean chamber or module, a beveledge etch chamber or module, a physical vapor deposition (PVD) chamberor module, a chemical vapor deposition (CVD) chamber or module, anatomic layer deposition (ALD) chamber or module, an atomic layer etch(ALE) chamber or module, an ion implantation chamber or module, a trackchamber or module, and any other semiconductor processing systems thatmay be associated or used in the fabrication and/or manufacturing ofsemiconductor wafers.

As noted above, depending on the process step or steps to be performedby the tool, the controller might communicate with one or more of othertool circuits or modules, other tool components, cluster tools, othertool interfaces, adjacent tools, neighboring tools, tools locatedthroughout a factory, a main computer, another controller, or tools usedin material transport that bring containers of wafers to and from toollocations and/or load ports in a semiconductor manufacturing factory.

An appropriate apparatus for performing the methods disclosed herein isfurther discussed and described in U.S. Pat. No. 8,728,956, issued onMay 20, 2014, and filed Apr. 11, 2011, and titled “PLASMA ACTIVATEDCONFORMAL FILM DEPOSITION”; and U.S. patent application Ser. No.13/084,305, filed Apr. 11, 2011, and titled “SILICON NITRIDE FILMS ANDMETHODS,” each of which is incorporated herein in its entireties.

The apparatuses and processes described herein may be used inconjunction with lithographic patterning tools or processes, forexample, for the fabrication or manufacture of semiconductor devices,displays, LEDs, photovoltaic panels and the like. Typically, though notnecessarily, such tools/processes will be used or conducted together ina common fabrication facility. Lithographic patterning of a filmtypically includes some or all of the following operations, eachoperation enabled with a number of possible tools: (1) application ofphotoresist on a workpiece, i.e., substrate, using a spin-on or spray-ontool; (2) curing of photoresist using a hot plate or furnace or UVcuring tool; (3) exposing the photoresist to visible or UV or x-raylight with a tool such as a wafer stepper; (4) developing the resist soas to selectively remove resist and thereby pattern it using a tool suchas a wet bench; (5) transferring the resist pattern into an underlyingfilm or workpiece by using a dry or plasma-assisted etching tool; and(6) removing the resist using a tool such as an RF or microwave plasmaresist stripper.

EXPERIMENTAL Experiment 1

An experiment was conducted for deposition of a silicon nitride (SiN)encapsulation layers. A first substrate including a 4:1 aspect ratiofeature was exposed to silane (SiH₄) and a mixture of nitrogen andammonia (N₂/NH₃) to deposit a SiN encapsulation layer. The step coverageachieved for the first substrate was 40%.

A second substrate including a 4:1 aspect ratio feature was exposed toSiH₄ and N₂/NH₃ continuously at 300° C. while plasma was pulsed between0 W and 500 W at a pulse frequency of 0.02 ms on and 1.98 ms off and aplasma frequency of 13.56 MHz to deposit a 300 Å SiN encapsulationlayer. The deposited film's bottom-to-top ratio was 68% andsidewall-to-top ratio was 71%. An example of the resulting substrate isshown in FIG. 9. FIG. 9 includes a substrate 901 with TEOS 903 and anSiN layer 905 deposited at low pressure and a silicon oxide film 907deposited by ALD. The silicon nitride layer 909 deposited by pulsedplasma PECVD as described herein is deposited conformally with a highstep coverage of 70% over the substrate.

Experiment 2

An experiment was conducted involving exposing a non-pulsedPECVD-deposited SiN encapsulation layer to periodic plasmapost-treatment. A substrate including a deposited SiN encapsulationlayer, which was deposited by non-pulsed PECVD, was exposed to plasmawith argon/helium post-treatment gas for a post-treatment operation fora duration of 30 seconds at a power of 2000 W and a plasma frequency of13.56 MHz. The substrate was exposed to the following sequence ofexposures: (a) plasma on for 0.02 ms, (b) plasma off for 1.98 ms, (c)repeat (a) and (b), (d) post-treatment using 10 s-60 s inert plasma, and(e) repeat (a)-(d).

The FTIR spectra for both the substrate with deposition only (dottedline) and the substrate with periodic plasma treatment (solid line) areshown in FIG. 10. As shown, the solid line shows a reduction in Si—Hbonds, which suggests a reduction in hydrogen content, and an increaseddensification peak, both of which indicate a higher quality filmresulting from the periodic plasma treatment.

Experiment 3

An experiment was conducted for exposing a non-pulsed PECVD-depositedSiN encapsulation layer to UV exposure post-treatment. A substrateincluding a deposited SiN encapsulation layer, which was deposited bynon-pulsed PECVD, was exposed to UV radiation at a wavelength of 180 nmto 600 nm for a duration of 300 seconds at a temperature of 300° C. TheFTIR spectra for both the substrate with deposition only (solid line)and the substrate with UV treatment (dotted line) are shown in FIG. 11.As shown, the dotted line shows a reduction in N—H bonds at 1101, whichsuggests a reduction in hydrogen content; a reduction in Si—H bonds at1103, which also suggests a reduction in hydrogen content; and anincreased densification peak at 1105. These characteristics suggest thata higher quality film resulted from the UV treatment.

Experiment 4

An experiment was conducted for deposition of encapsulation layers usingremote plasma chemical vapor deposition at 250° C.

An encapsulation layer was deposited on a first substrate including a4:1 aspect ratio feature in an RPCVD chamber including a showerhead byintroducing nitrogen radicals from a remote plasma to the substrate witha silane delivered to the substrate downstream of the showerhead withthe pedestal holding the substrate set to a temperature of 250° C. Thestep coverage of the deposited film was greater than 80%.

A SiCO encapsulation layer deposited on a second substrate including a7:1 aspect ratio feature in an RPCVD chamber including a showerhead byintroducing radicals from a remote plasma to the substrate with asilicon-containing precursor delivered to the substrate downstream ofthe showerhead with the pedestal holding the substrate set to atemperature of 250° C. FIG. 12A shows the substrate before performing awet etch rate experiment. Substrate 1200 with an underlayer 1201 andTEOS 1203, with a SiN layer 1207 deposited at low pressure and SiCOencapsulation layer 1209 deposited conformally over the substrate. Notethe conformality shown at arrow 1219.

The substrate was exposed to a 100:1 diluted HF solution for 5 minutes.FIG. 12B shows the substrate 1220 after this exposure. As shown, the topof the feature and at the sidewalls as indicted by arrow 1229 showed noetching, thereby suggesting that the wet etch rate is nearly 0 for thedeposited encapsulation layer 1209.

Experiment 5

An experiment was conducted for encapsulation layers deposited byvarious methods. Substrates were subjected to four methods ofdeposition. The first method involved exposure to continuous plasmausing conventional PECVD (continuous exposure to silicon-containingprecursor and second reactant with continuous plasma) with nopost-treatment. Plasma power was set to 500 W with a plasma frequency of13.5 MHz. This method is indicated in FIGS. 13A and 13B as the whitebars (1302).

The second method involved pulsed PECVD (continuous exposure tosilicon-containing precursor and second reactant with pulsed plasma)with no post-treatment. Plasma was pulsed between 0 W and 500 W withduty cycle of 10% with pulsing frequency of 500 Hz. This method isindicated in FIGS. 13A and 13B as the diagonally striped bars (1304).

The third method involved pulsed PECVD (continuous exposure tosilicon-containing precursor and second reactant with pulsed plasma)with periodic plasma post-treatment. Plasma during pulsed plasmadeposition was pulsed using 0.2 ms RF on/1.8 ms RF off pulses between 0W and 500 W at a pulse frequency of 500 Hz. Plasma during periodicplasma post-treatment was turned on for a duration of 60 seconds at aplasma power of 2000 W (4-station, power density=0.6 W/cm²) and plasmafrequency of 13.56 MHz. This method is indicated in FIGS. 13A and 13B asthe horizontally striped bars (1306).

The fourth method involved exposure to continuous plasma usingconventional PECVD (continuous exposure to silicon-containing precursorand second reactant with continuous plasma) with periodic plasmapost-treatment. Plasma power was set to 500 W with a plasma frequency of13.56 MHz. Film was deposited using continuous plasma for few seconds todeposit 25 Å-30 Å. This film was then exposed to periodic plasmapost-treatment which was turned on for a duration of 60 seconds at aplasma power of 2000 W and plasma frequency of 13.56 MHz. This cycle wasrepeated until the entire film thickness was achieved. This method isindicated in FIGS. 13A and 13B as the shaded bars (1308).

The process conditions for Process Conditions A, B, and C as indicatedin FIGS. 13A and 13B, are outlined in Table 1 below.

TABLE 1 Process Conditions for Deposition Portion A B C Precursor SiH₄800 sccm SiH₄ 75 sccm SiH₄ 100 sccm Reactant NH₃ 800 sccm NH₃ 50 sccmNH₃ 2125 sccm N₂ = 20000 N₂ = 16000 N₂ = 16000 Film Deposited SiN SiNSiN Inert/Carrier Gas None None None Substrate 300° C. 400° C. 400° C.Temperature Chamber Pressure 1.5 Torr 7 Torr 9 Torr HF 13.5 MHz Yes YesYes LF 400 KHz Yes No No

FIG. 13A shows the resulting hydrogen content for substrates exposed toeach set of process conditions and deposited by each of the fourmethods. For Process Conditions A, the hydrogen content for thesubstrate subjected to periodic plasma treatment was less than that ofpulsed plasma with periodic plasma treatment, and both the hydrogencontent for these two methods were less than the hydrogen content ofsubstrates subjected to continuous plasma and pulsed plasma withoutpost-treatment. This suggests that periodic plasma post-treatmentreduces hydrogen content, and further that pulsed plasma withpost-treatment may be a viable and suitable option in some embodiments.

For Process Conditions B, hydrogen content for the substrate subjectedto pulsed plasma was the highest, which suggests that at hightemperature (400° C.), pulsed plasma may not be suitable in someembodiments, but the combination of pulsed plasma with periodic plasmatreatment substantially decreased the hydrogen content. Periodic plasmatreatment alone also resulted in a low hydrogen content. These resultssuggest that the combination of pulsed plasma deposition with periodicplasma treatment, or periodic plasma treatment alone can result in a lowhydrogen content film even if deposited at 400° C.

For Process Conditions C, hydrogen content for both continuous plasmaand pulsed plasma substrates were high, but combining either of thosewith periodic plasma treatment resulted in a substantial decrease ofhydrogen content, which further supports that for some embodiments, evenif substrates are deposited at 400° C., periodic plasma treatment may besuitable for reducing hydrogen content. The results indicate thatpost-treatment reduces the hydrogen content and wet etch rate.

FIG. 13B shows the resulting wet etch rate for each of the substrates inFIG. 13A when subjected to a 200:1 hydrogen fluoride etchant. ForProcess Conditions A, the wet etch rate for substrates withencapsulation layers deposited by pulsed plasma, pulsed plasma withperiodic plasma treatment, and periodic plasma treatment were lower thanthe wet etch rate of the substrate with an encapsulation layer depositedby continuous plasma. The wet etch rate for encapsulation layersdeposited and subjected to periodic plasma treatment was even lower thanthat of pulsed plasma deposited encapsulation layers withoutpost-treatment. A lower wet etch rate suggests that the quality of thefilm is higher and thus can withstand exposure to harsher conditions insubsequent processing, thereby allowing the encapsulation layer toeffectively protect an underlying memory stack.

For Process Conditions B, a similar trend is shown, as encapsulationlayers that were also subjected to periodic plasma treatment resulted ina lower wet etch rate than layers that did not undergo post-treatment.Likewise, for Process Conditions C, a similar trend is also shown, withthe wet etch rate for encapsulation layers deposited and subjected toperiodic plasma treatment having a substantially lower wet etch ratethan layers that were not subjected to periodic plasma treatment.

CONCLUSION

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, it will be apparent thatcertain changes and modifications may be practiced within the scope ofthe appended claims. It should be noted that there are many alternativeways of implementing the processes, systems, and apparatus of thepresent embodiments. Accordingly, the present embodiments are to beconsidered as illustrative and not restrictive, and the embodiments arenot to be limited to the details given herein.

What is claimed is:
 1. A method of encapsulating a memory device on asubstrate, the method comprising: (i) exposing the substrate having thememory device to a deposition precursor and a reactant at a substratetemperature less than 300° C.; and (ii) igniting a plasma to deposit anencapsulation layer over the memory device, the encapsulation layerbeing hermetic and having a hydrogen content less than 15%.
 2. Themethod of claim 1, further comprising exposing the encapsulation layerto a post-treatment process at a temperature less than 300° C.
 3. Themethod of claim 1, wherein the encapsulation layer is selected from thegroup consisting of silicon nitride, undoped silicon carbide,oxygen-doped silicon carbide, germanium nitride, undoped germaniumcarbide, and oxygen-doped germanium carbide.
 4. The method of claim 1,further comprising pulsing the plasma to deposit the encapsulationlayer.
 5. The method of claim 4, wherein the pulses of plasma have apulse duration between about 0.02 ms and about 5 ms.
 6. The method ofclaim 4, wherein the plasma is pulsed at a pulsing frequency betweenabout 100 Hz and about 6 Hz.
 7. The method of claim 1, wherein theencapsulation layer is deposited by remote plasma enhanced chemicalvapor deposition.
 8. The method of claim 7, wherein remote plasmaenhanced chemical vapor deposition comprises: (a) flowing the reactantto a remote plasma-generating region and igniting the plasma to generatereactant radicals; (b) introducing the reactant radicals through ashowerhead to the substrate; and (c) introducing the depositionprecursor downstream of the showerhead to the substrate whileintroducing the reactant radicals.
 9. The method of claim 2, wherein thepost-treatment process comprises exposing the substrate to apost-treatment gas and igniting a second plasma without a reactant. 10.The method of claim 9, wherein the substrate is exposed to thepost-treatment gas and the second plasma for a duration between about 10seconds and about 50 seconds.
 11. The method of claim 9, wherein thepost-treatment gas is selected from the group consisting of nitrogen,ammonia, helium, argon, and combinations thereof.
 12. The method ofclaim 2, wherein the post-treatment process comprises exposing thesubstrate to ultraviolet radiation.
 13. The method of claim 1, whereinthe memory device is a magnetoresistive random-access memory.
 14. Themethod of claim 1, wherein the memory device comprises a magnetic tunneljunction.
 15. The method of claim 1, wherein the encapsulation layer isdeposited to a thickness between about 50 Å and about 500 Å.
 16. Themethod of claim 1, wherein the encapsulation layer is deposited byplasma enhanced chemical vapor deposition.
 17. The method of claim 1,wherein the encapsulation layer deposited over the memory device has astep coverage between about 70% and about 90%.
 18. The method of claim1, wherein the encapsulation layer is a silicon nitride film depositedby exposing the substrate to a silicon-containing precursor and anitrogen-containing reactant.
 19. The method of claim 1, wherein theencapsulation layer is a silicon carbide film deposited by exposing thesubstrate to a silicon- and carbon-containing precursor and hydrogen.20. The method of claim 1, further comprising prior to depositing theencapsulation layer, heating the substrate to a temperature of about300° C.